Solid state relays are being substituted for older style, obsolescent track relays in alternating current (AC)track circuits, particularly where a shift in the frequency of electric propulsion power is planned. One such relay arrangement is disclosed in my U.S. Pat. No. 4,188,002, issued Feb. 12, 1980 for a "Vital Power Varistor Circuit for Railroad Signaling Systems". Normally such track circuits are energized with a steady alternating current, obviously of the frequency to which the solid state track relay apparatus is tuned and to which it responds. In some locations, however, the track current must be coded when the corresponding track section is occupied to activate and control cab signal apparatus on board the train. When the train clears the section, the track circuit must then reset to steady energy. However, many of the solid state relay units, particularly the one disclosed in the cited patent, are not designed to fully respond to coded current to detect a departure of the train. Some additional element or apparatus must be provided to assist or actuate the solid state relay to respond to coded energy to initiate the reset or restoration of the track circuit to steady current. Obviously, such additional apparatus must be compatible with the solid state relay arrangement and of simple, efficient, yet reliable and vital design.
Accordingly, an object of my invention is code reset apparatus for railroad track circuits which include a solid state track relay arrangement.
Another object of the invention is a circuit network for detecting coded track current, following the passage of a train through a track circuit, to actuate a response by a solid state track relay which initiates the reset of the track circuit to restore its normal steady energy condition.
A further object of the invention is apparatus supplementing a solid state track relay means in an alternating current track circuit and which stores energy from successive code pulses received following the passage of a train through the track section and discharges that stored energy so synchronized as to augment the code pulses to sufficiently energize the track relay, which is nonresponsive to coded energy, to actuate a response which restores the track circuit to a steady energy condition.
Yet another object of my invention is code reset apparatus for an AC track circuit, which is normally supplied with steady energy from the source and is supplied with coded energy during the passage of a train through the section, including a timing circuit which accumulates a charge from the code pulses received from the track circuit source, a switching circuit responsive, when complete, to a predetermined level of stored timing energy to energize a first relay, a second relay connected to respond to the code pulses from the source to periodically complete the switching circuit at the end of each code pulse so that the first relay is energized during a code off-period, an analog storage network accumulating voltage signals from the track relay means, as code pulses are received through the track and line circuit, and controlled by the first relay to release its energy storage to supplement the energy received by the track relay during coding operation and initiate a reset of the track circuit transmitter to steady energy.
Other objects, features, and advantages of my invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings.